JPH0153864B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new process for producing iminodiacetate from diethanolamine. More specifically, the present invention relates to characteristic reaction conditions, additives, and catalysts for producing iminodiacetate by reacting diethanolamine in the presence of an alkali metal hydroxide.

For example, the production of sodium iminodiacetate from diethanolamine proceeds according to reaction formula [1] shown below, and the production of iminodiacetic acid from sodium iminodiacetate proceeds according to reaction formula [2].

Iminodiacetate is usually neutralized to form iminodiacetic acid, and in addition to various uses that utilize its chelating action,
It is widely used as a raw material for agricultural chemicals, medicines, etc.

As an industrial method for producing iminodiacetates, a method using hydrocyanic acid and formaldehyde as main raw materials is generally known today. However, since hydrocyanic acid is a highly poisonous gas, there are major restrictions in terms of manufacturing equipment, handling, and location.Furthermore, since most of the hydrocyanic acid is obtained as a by-product during the production of acrylonitrile, there are also major problems in securing a stable supply of raw materials.

On the other hand, a method for producing iminodiacetate by oxidative dehydrogenation of diethanolamine in a caustic alkali is disclosed in US Pat. No. 2,384,817 and US Pat. No. 3,842,081. U.S. Patent No. 2384817 is 1
This patent uses cadmium as a catalyst in a method of dehydrogenating alcohols with a strong alkali to produce carboxylic acid salts.

Further, in the method disclosed in Example 1 of US Pat. No. 3,842,081, a yield of sodium iminodiacetate of 84.5% is obtained by reacting diethanolamine in the presence of a cadmium oxide catalyst at high temperature for a short period of time.

However, since both patents use cadmium as a catalyst, cadmium, which is a toxic substance, may mix into products or cause major social problems if it flows into rivers as wastewater, so cadmium is not used as an industrial catalyst. I have a problem using it.

As a method for producing iminodiacetate that does not use hydrocyanic acid, the present inventors have conducted intensive research on the oxidative dehydrogenation method of diethanolamine. As a result, the present inventors have found that iminodiacetic acid can be produced in high yield without using cadmium compounds, which have toxicity problems. We have discovered a new method for producing salt and completed the present invention.

The present invention relates to a method for producing iminodiacetate, which comprises reacting diethanolamine with an alkali metal hydroxide, water and copper in the presence of a zirconium-containing catalyst.

A feature of the present invention is that when producing iminodiacetate from diethanolamine, a safe catalyst containing copper and zirconium is used without using a cadmium catalyst.

Even if the copper-containing catalyst is not supported on zirconium oxide, by using it under very mild conditions of 120 to 220°C, the yield of iminodiacetate can be 90 to 95 mol % based on diethanolamine. However, the catalyst containing copper and zirconium not only has the effect of improved heat resistance and longer catalyst life, but also improves selectivity and catalytic activity, resulting in an iminodiacetate yield of 90-96 mol%, 10 in temperature
It became possible to lower the temperature by ~20℃. By carrying out the present invention, it has become possible to improve the yield of iminodiacetate, shorten the reaction time, and use milder reaction conditions as compared to conventional methods. As a result, we have completed a revolutionary method for producing iminodiacetate using oxidative dehydrogenation of diethanolamine, which enables a significant reduction in the production cost of iminodiacetate and is easy to implement industrially.

In one embodiment of the present invention, the catalyst used in the method of the present invention contains copper and zirconium as essential components. The catalyst can be used as it is or supported on an alkali-resistant carrier. The amount of catalyst used ranges from 1 to 70% by weight, preferably from 10 to 30% by weight, based on diethanolamine.

The copper- and zirconium-containing catalyst of the present invention uses nitrate as a raw material compound of copper or zirconium,
Examples include inorganic salts such as sulfates, carbonates, oxides, halides, and hydroxides, and organic salts such as acetates, oxalates, citrates, and lactates. In particular, highly water-soluble salts are preferred.

Although the form of the catalyst is not particularly limited, an alkaline aqueous solution is added to a solution of a copper compound and a zirconium compound dissolved in water to precipitate the hydroxide, the precipitate is washed with water, and after drying, it is exposed to air or oxygen. Copper- and zirconium-containing catalysts that have been oxidized in a hydrogen atmosphere and then reduced in a hydrogen atmosphere are preferred. Moreover, a catalyst in which zirconium oxide is impregnated with an aqueous solution of a copper compound, dried, oxidized in air or oxygen, and then reduced in a hydrogen atmosphere and supported on zirconium oxide is preferably used.

Since the activity of the catalyst usually decreases little due to reaction, it can be used repeatedly, but it can also be used once.

Water in the reaction of the present invention was initially thought to promote the decomposition of imino groups, but under the mild reaction conditions of the present invention, the decomposition of imino groups was very small, and rather it promoted the decomposition of diethanolamine and alkali metal hydroxide. It has the advantage of being able to react in a homogeneous system, which is essential for obtaining iminodiacetates in high yields. The amount of water used in the reaction is 10% by weight or more, preferably 100 to 500% by weight based on diethanolamine.
is within the range of

The alkali metal hydroxide used in the present invention includes lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide. Among these, sodium hydroxide and potassium hydroxide are particularly preferably used. The amount of alkali metal hydroxide used is at least the equivalent equivalent to the conversion rate of diethanolamine used in the reaction, preferably
It is in the range of 1.0 to 2.0 equivalents. As the alkali metal hydroxide, any of flakes, powders, pellets, etc. and aqueous solutions thereof can be used, but aqueous solutions of alkali metals are generally preferably used because they are convenient in terms of handling.

Diethanolamine is preferably of high purity in order to avoid contamination of the iminodiacetate with impurities.
There are no particular restrictions on purity, but usually
The amount used is 96% by weight or more, preferably 99% by weight or more.

The reaction temperature is 220°C or less, usually 120 to 200°C, to prevent thermal decomposition and hydrogenolysis of the NH group of diethanolamine and the NH group of iminodiacetate.
Preferably, the temperature range is 140 to 190°C.
Additionally, some of the surfaces of copper and zirconium catalysts begin to sinter at temperatures exceeding 220°C, reducing the surface area and decreasing catalytic activity. More preferred.

Since the reaction is an oxidative dehydrogenation reaction, it is preferable to lower the reaction pressure as much as possible from the viewpoint of reaction rate. Usually, the pressure is higher than the minimum pressure for proceeding the reaction in a liquid phase, preferably in the range of 0 to 20 kg/cm ² G, more preferably 5 to 15 kg/cm ² G.

The reaction time can be selected as appropriate and depends on the reaction temperature, amount of catalyst, and reaction pressure. For example, reaction temperature
In the case of 155° C., reaction pressure of 10 Kg/cm ² G, and a catalyst amount of 10% by weight based on diethanolamine, the reaction time is 3 to 5 hours.

As for the reaction format, any of batch, semi-batch and continuous reaction methods can be used.

EXAMPLES Hereinafter, embodiments of the present invention will be specifically illustrated and explained with reference to Examples. The present invention is not limited to these examples.

Here, the conversion rate of diethanolamine and the selectivity of iminodiacetate are derived from the following equation.

Conversion rate of diethanolamine (%) = Number of moles of diethanolamine reacted / Number of moles of diethanolamine subjected to reaction x 100 Selectivity of iminodiacetate (%) = Number of moles of iminodiacetate produced / Number of moles of diethanolamine reacted ×10
0 Example 1 Diethanolamine 80.0g, sodium hydroxide
To a solution of 64.0 g, 170.0 g of water, and 24.8 g of zirconium oxychloride and 4.0 g of copper nitrate as catalysts dissolved in 300 ml of water, an aqueous sodium hydroxide solution was added to precipitate the hydroxide, and the precipitate was washed with water and dried.
Heat treated in air at 500℃ for 3 hours, heated to 230℃ in hydrogen stream
8.0 g of the copper- and zirconium-containing catalyst obtained by reduction treatment at 160°C for 6 hours was charged into a 500ml autoclave, and the interior was replaced with hydrogen gas ^three times. The reaction was continued until no generation occurred. The time required for the reaction is
The temperature was 4.0 hours after the temperature was raised to 160°C. After the reaction was completed, the reaction solution was taken out and analyzed, and the conversion rate of diethanolamine was 97.7 mol%, and the selectivity of iminodiacetate was 96.0 mol%.

Example 2 Diethanolamine 80.0g, sodium hydroxide
64.0 g, 170.0 g of water, and 10 g of zirconium oxide as a catalyst were impregnated with an aqueous solution containing 4.2 g of copper nitrate, and after drying, heat treated in air at 500°C for 3 hours,
8.0 g of a catalyst obtained by reducing copper on zirconium oxide at 230°C in a hydrogen stream for 6 hours was
ml, was charged into an autoclave, and after internal purge with hydrogen gas three times, the reaction temperature was 160℃, and the reaction pressure was 9Kg/
The reaction was carried out until no more hydrogen was produced at cm ² g. The time required for the reaction was 4.2 hours after the temperature was raised to 160°C. After the reaction was completed, the reaction solution was taken out and analyzed, and the conversion rate of diethanolamine was 97.7 mol%, and the selectivity of iminodiacetate was 95.7 mol%.

Example 3 In order to check the repeated activity of the catalyst, repeated experiments were conducted under the same reaction conditions as in Example 1.
The reaction time required for the 10th reaction was 5.0 hours after the temperature was raised. After the reaction was completed, the reaction solution was taken out and analyzed, and the conversion rate of diethanolamine was 96.2.
The selectivity of iminodiacetate was 94.2 mol%.

Claims (1)

[Claims] 1. A method for producing iminodiacetate, which comprises reacting diethanolamine with an alkali metal hydroxide, water, and copper in the coexistence of a zirconium-containing catalyst.